By the middle of yesterday afternoon, in the glum silver light of a pouring-down rain, with the temperature dropping and winter coming back, the crowds started to scream, clap, cheer and shout "Thank you!" and "Goodbye!" For days they'd been so quiet -- solemn as children watching sharks cruise around and around in an aquarium tank as they studied the grim weight of Gorbachev's motorcades sliding by. And now:

"Do svidaniye, Gorby!" shouted a woman named Spencer DeWitt, of Arlington, who had waited in the rain on the corner of Connecticut and L for half an hour to see him ride back from his final meeting with President Reagan.

Goodbye, goodbye. And the screaming faces, astonished and gratified at the same time to see him go past, women hugging each other, men staring after him with that wondering preoccupation you see at the end of big football games ... "He looked right at me!" said one woman, in an echo of the faith held by any number of millions who have waited for Bruce Springsteen, Bobby Kennedy, anyone who fascinates.

Even Officer Reamer Shedrick of D.C. Police, who has seen them come and go, was grinning, nodding and saying, "Exciting. Very exciting."

He looked right at me ... A few hours earlier, before the rain started, Gorbachev had astonished another crowd at the corner of Connecticut and L by stopping his limousine and getting out to shake hands, smile, wave and say, "World peace."

"He picked me out, man, what can I say," said Patricia Terry, an account executive at Wang Laboratories Inc., with fierce, bright, head-shaking self-absorption, as if she couldn't quite believe it.

Said Duke Zeibert, who came out on the balcony of his restaurant when he heard the racket, Gorbachev "caught my eye and waved to me. I'm 76 years old and it takes a lot to get me excited, but I was excited. I'm still excited."

"I've seen a lot of motorcades, but never did one stop and talk to me," said Leslie Kobylinski, a media relations employe at the U.S. Chamber of Commerce. "Talk about the consummate public relations man."

Looked right at me ... What was going on here, that three hours later people would be crowding the same corners in the preposterous belief that he'd do the same thing, that he'd get out of the car, say, and accept the gift of irises that Hilary House, a law firm librarian, had originally bought for herself, until she realized "I could give them," and stood on the curb with her wet hair hugging her scalp in order to make her offering when he came back from the farewell ceremonies at the White House? If he came back this way ...

He did, behind the great procession of eight motorcycles, of cop cars and limousines that had been cruising downtown Washington for days, except the crowd wasn't solemn anymore, it was screaming, that strange, wildly human combination of gasp and a thin noise like cellophane tearing, the sonic equivalent of goose bumps.

Was it the smile? He leaned into the window and waved and smiled, not that little smile that he smiles when he's pondering what to say and seeming to savor his own thoughts, the way he might taste a wine; nor was it a courteous smile, or even a grateful one. It was a smile that any of America's presidential candidates would kill for, a smile of happy conspiracy that says, "It's them, they're the ones who ruin everything, but you and I, we understand, we're the only ones, and we know" ...

Right at me ... It may be the most seductive political smile since Eisenhower's, except that Eisenhower's smile told you that he was a nice guy, while Gorbachev's smile, behind the bulletproof glass in the limousine, told you that you were both nice guys, you and he. This was especially alluring when you consider that we have also feared him. As Soviet elder statesman Andrei Gromyko said, "This man has a nice smile, but he has teeth of iron." So every smile is a gift and a surprise.

Gorbachev had already proved himself a master of surprise at the Reykjavik summit, with his press conferences in Europe, with his ability to speak without the cue cards and script that prop up Reagan's every planned appearance. How bizarre! It's the Russians who are supposed to be hamstrung by ideology, puppets of historical inevitability, the sort of automatons that we saw battling Sylvester Stallone in "Rocky IV."

But here he was, an unrobotic hour and a half late to the White House already, and he'd stopped his Zil limousine so abruptly that the car in back of him had to brake hard to avoid a collision, and he'd gotten out to shake hands with people -- but not without pausing to straighten his necktie, said George Purcell, the owner of an office-supply store.

A real pro. Right at me ...

At the same time we think the Soviets are robots, we think of them as beasts, in the manner of fat, warty, bragging Khrushchev pounding his shoe on the desk at the United Nations. Gorbachev was clearly not that either. In fact, the whole Soviet delegation seemed out to disprove every stereotype.

They weren't all burly, they didn't all wear leather coats, they didn't mob buffet tables and belly up to bars. At one reception, they didn't even smoke their famous foul-smelling cigarettes. There may have been a certain dysplastic quality to their clothing, the odd collar hanging loose, the shoes the peculiar gray of something floating in a New Jersey river, the eyeglasses that never looked quite right, as if they'd borrowed them from their spouses to look up a phone number ... But you couldn't always pick them out on the street.

Gorbachev was, of all strange things in America nowadays, a politician who was unpredictable. The president, for instance, is the master of the perfectly organized media happening, the agreed-upon ritual -- it's as if Reagan, decades ago, had asked us what we wanted him to be and he'd become it, and his very existence was a bargain. There's a sense of plaintive compromise about him that you see in movie and television stars. There was nothing plaintive or compromised about Gorbachev, and the staging only showed itself in the occasional necktie-straightening. Gorbachev looked young, fresh, self-assured, with no democratic mock-humility, and very possibly not much democratic humility of any kind.

But he had that smile, he had those surprises, he had the INF Treaty.

Gorbachic! Gorbymania! Or, as Secretary of Education William Bennett said, warning of overenthusiasm, "Gorbasms!"

Of course, it was interesting to note that at the last major public appearance of his visit, the press conference at the new Soviet compound on Tunlaw Road, the atmosphere, at least on television, was very Communist -- the huge bank of Soviet officialdom at the dais, a questioner singled out with a curt "Okay, you," an opening statement by Gorbachev of 1 hour 10 minutes 39 seconds. A row of officials, the European formality of the Austrian curtains behind them, and in front, the precise placement of potted poinsettias, hard and regular, teeth of iron.

Right at us.